Re: [PATCH 1/1] drm/amdgpu: Drop eviction lock when allocating PT BO

[Christian König <christian.koenig@xxxxxxx>]

Am 02.11.22 um 22:10 schrieb Philip Yang:
> Re-take the eviction lock immediately again after the allocation is
> completed, to fix circular locking warning with drm_buddy allocator.
>
> Move amdgpu_vm_eviction_lock/unlock/trylock to amdgpu_vm.h as they are
> called from multiple files.
>
> Signed-off-by: Philip Yang <Philip.Yang@xxxxxxx>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c    | 26 -----------------------
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h    | 26 +++++++++++++++++++++++
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c |  2 ++
>   3 files changed, 28 insertions(+), 26 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index 2291aa14d888..003aa9e47085 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -143,32 +143,6 @@ int amdgpu_vm_set_pasid(struct amdgpu_device *adev, struct amdgpu_vm *vm,
>   	return 0;
>   }
>   
> -/*
> - * vm eviction_lock can be taken in MMU notifiers. Make sure no reclaim-FS
> - * happens while holding this lock anywhere to prevent deadlocks when
> - * an MMU notifier runs in reclaim-FS context.
> - */
> -static inline void amdgpu_vm_eviction_lock(struct amdgpu_vm *vm)
> -{
> -	mutex_lock(&vm->eviction_lock);
> -	vm->saved_flags = memalloc_noreclaim_save();
> -}
> -
> -static inline int amdgpu_vm_eviction_trylock(struct amdgpu_vm *vm)
> -{
> -	if (mutex_trylock(&vm->eviction_lock)) {
> -		vm->saved_flags = memalloc_noreclaim_save();
> -		return 1;
> -	}
> -	return 0;
> -}
> -
> -static inline void amdgpu_vm_eviction_unlock(struct amdgpu_vm *vm)
> -{
> -	memalloc_noreclaim_restore(vm->saved_flags);
> -	mutex_unlock(&vm->eviction_lock);
> -}
> -
>   /**
>    * amdgpu_vm_bo_evicted - vm_bo is evicted
>    *
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> index 83acb7bd80fe..02240dc2f425 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> @@ -495,4 +495,30 @@ static inline uint64_t amdgpu_vm_tlb_seq(struct amdgpu_vm *vm)
>   	return atomic64_read(&vm->tlb_seq);
>   }
>   
> +/*
> + * vm eviction_lock can be taken in MMU notifiers. Make sure no reclaim-FS
> + * happens while holding this lock anywhere to prevent deadlocks when
> + * an MMU notifier runs in reclaim-FS context.
> + */
> +static inline void amdgpu_vm_eviction_lock(struct amdgpu_vm *vm)
> +{
> +	mutex_lock(&vm->eviction_lock);
> +	vm->saved_flags = memalloc_noreclaim_save();
> +}
> +
> +static inline int amdgpu_vm_eviction_trylock(struct amdgpu_vm *vm)
> +{
> +	if (mutex_trylock(&vm->eviction_lock)) {
> +		vm->saved_flags = memalloc_noreclaim_save();
> +		return 1;
> +	}
> +	return 0;

While at it please make the return value bool and return true/false here.

Apart from that the patch is Reviewed-by: Christian König 
<christian.koenig@xxxxxxx>

Thanks,
Christian.

> +}
> +
> +static inline void amdgpu_vm_eviction_unlock(struct amdgpu_vm *vm)
> +{
> +	memalloc_noreclaim_restore(vm->saved_flags);
> +	mutex_unlock(&vm->eviction_lock);
> +}
> +
>   #endif
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
> index 358b91243e37..b5f3bba851db 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
> @@ -597,7 +597,9 @@ static int amdgpu_vm_pt_alloc(struct amdgpu_device *adev,
>   	if (entry->bo)
>   		return 0;
>   
> +	amdgpu_vm_eviction_unlock(vm);
>   	r = amdgpu_vm_pt_create(adev, vm, cursor->level, immediate, &pt);
> +	amdgpu_vm_eviction_lock(vm);
>   	if (r)
>   		return r;
>